Action Points

Note that this small, randomized trial of stationary bike-riding for pregnant women with a history of GDM found no difference between intervention and usual care with regards to recurrent GDM.

Some cardiovascular measures were improved however.

Supervised home-based exercise initiated at 14 weeks of gestation did not prevent the recurrence of gestational diabetes, but it was tied to fitness and psychological benefits for the mother, Australian researchers reported.

The single-centered, randomized study of 180 pregnant women found no significant difference in the rate of recurring gestational diabetes mellitus (GDM) with a home-based, stationary cycling program (40.5% versus 40% for controls, P=0.95), according to Kym Guelfi, PhD, of the University of Western Australia in Perth, and colleagues.

However, maternal fitness was improved and psychological distress was decreased post-intervention, they wrote in Obstetrics & Gynecology.

"We know that regular exercise is really important for the prevention of type 2 diabetes, but whether it can prevent GDM is less clear," Guelfi, told MedPage Today. "We wanted to develop and test an exercise program that removed many of the barriers to exercise during pregnancy -- by placing a stationary bike in each woman's home and visiting her in the comfort of her own home three times per week. We were trying to overcome issues with childcare, difficulties with travel, outside weather conditions, and an overall lack of time."

The risk of recurring diabetes was about 55% among women at their institution, King Edward Memorial Hospital in Perth, the authors noted.

Gestational diabetes is associated with pregnancy complications, as well as an increased risk of type 2 diabetes and metabolic syndrome in both mother and offspring later in life. Because past research on physical activity has been linked to a reduced risk of gestational diabetes, the authors wanted to examine this relationship further, noting that an exercise intervention program has not been studied before in regards to recurring risk.

Recruited from antenatal clinics, obstetricians, general practitioners, and ultrasound practices, pregnant women who experienced gestational diabetes in a past pregnancy were enrolled in the study, conducted from 2011 to 2014. The participants, between weeks 12-14 of pregnancy, were equally divided into the a 14-week exercise interventional program and a control group.

One week following randomization, the intervention group began an at-home, stationary cycling exercise program, under the direct supervision of an exercise physiologist.

At least 48 hours following the last exercise session, the participants completed a fasting, 75-g oral glucose tolerance test (OGTT) test to compare to their baseline, pre-intervention levels. The researchers defined gestational diabetes as a fasting venous blood glucose of 5.5 mmol/L or greater (99 mg/dL), or a 2-hour OGTT glucose 8.0 mmol/L or greater (144 mg/dL), or both. Insulin sensitivity was also measured by the insulin sensitivity index and homeostatic model of assessment.

Guelfi's group reported exercise had no impact on the rate of recurrence (relative risk 1.01, 95% CI 0.70-1.46, P=0.950) or the severity of gestational diabetes. Similarly, the study intervention did not significantly change glucose intolerance or insulin sensitivity with glucose 2 hours post-OGTT for the exercise group coming at 7.6 mmol/L versus 7.7 mmol/L for the control group (P>0.05).

The authors noted the maternal fitness and psychological benefits of exercise throughout pregnancy are noteworthy.

"Regardless, the improvement in fitness and psychological well-being are still very important outcomes in the present study – and we know from our previous work that for women that are already diagnosed with GDM, exercise is really beneficial for managing blood glucose levels," Guelfi said.

Study limitations included the fact that data on daily nutritional intake was gathered with self-reported food diaries, and that the optimal duration and intensity of exercise for the prevention of gestational diabetes is not known.

"It must also be noted that the exercise group gave birth to significantly more male neonates. This coincidental occurrence may have influenced the rate of GDM given that women carrying a male fetus may have an increased risk of GDM," the authors pointed out.

The authors stated that in future studies, the exercise intervention should be implemented earlier in pregnancy, because it's been suggested that "placental function and gene expression are programmed by the first trimester."

"While the program did not prevent the recurrence of GDM, it is important to note that we specifically studied woman that had GDM in a previous pregnancy (as they are at the highest risk of recurrence)," Guelfi told MedPage Today. "Whether the program would prevent GDM in women during their first pregnancy remains to be tested. It is also possible that commencing regular exercise after the first trimester of pregnancy is too late, so it is important that future studies examine the benefits of exercise commenced earlier in pregnancy and even pre-conception if possible."

The study was funded by the National Health and Medical Research Council of Australia.

Guelfi and co-authors disclosed no relevant relationships with industry.

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